Treating wood



M. S. HUDSON Jan. 16, 1951 TREATING WOOD Filed Nov. 2, 1946 PatentedJan. 16, 1 951- UNITED STATE S PATENT OFFICE product has numerousadvantages, among which may be mentioned the ease with'which apotentially reactive'resin may be incorporated'in the same and' thestability of the wood product when exposed to moisture.

The primary object of the invention'is the provision of an improvedrapid, economical and reliable process for producing such a completelydried hydrolyzed wood in massive or comminuted form, or in the form ofpowderor flour suitable for molding purposes. This process employs (1)hydrolyzing during which condensates from the steam and'products of thehydrolysis reac-, tion soluble therein are constantly removed fromcontact with the wood and from the treating chamber, and (2) the dryingof such hydrolyzed wood in an atmosphere of an'organic drying mediumwhich is a solvent for organic solvent soluble extractives produced bythe hydrolysis or already present in the wood whereby the same areremoved from the wood. In other words, the

process assures that the condensates from steam and hydrolysis productssoluble therein are continually removed during hydrolysis whereby suchvaluable by-products may be recovered in a form free from de radationand that objectionable organic solvent soluble extractives produced byhydrolysis or already present are simultaneously removed in the dryingoperation incident to forming woocl'having a zero moisture content.

In the manufacture of hydrolyzed products in accordance with theinvention from Wood in the form of structural lumber, plywood andcomminuted wood and similar materials, the same is subjected to a'vaportreatment with either steam containing small amounts of hydrochloricacid, as a'c'atalyst, or steam with small amounts of aniline to producemild hydrolysis 'for the purpose of removing hemicelluloses. After thisvapor treatment, pressure with air or inert gas may be built up in thewood in the treating chamher; The treating chamber is then filled withwater still maintaining the pressure of inert gas resentative examplesof 2 or air, as in the Rueping process (see United States Patent No.709,799, Reissue No. 12,707, and Patent No. 1,008,864). Water is driveninto the wood by employing a higher pressure, and this water serves towash out the hydrolysis products on the release of the pressure andinstitution of vacuum or suitable reduced pressure conditions. One ormore of these cycles may be employed for completely washing out thehydrolysis products from the wood. The wood may then be driedbyemploying vapor phase drying, as described in my Patent No. 2,273,039and my application Serial No. 579,851, now Patent No. 2435218, using asuitable drying medium such as Stoddard solvent. As disclosed in myabove identified patents, in efiecting dehydration of wood any suitableorganic material which can be vaporized and which vapor-will permeatewet wood and flash-off the moisture content thereof withoutdeleteriously affecting the wood may be.

used. There are numerous and practically unlimited examples of suitablematerials, but repsatisfactory materials are as follows:

Organic compounds, whether saturated or unsaturated, chain or cyclic,and any of their homologues that might be suitable for this procedure,such as alcohols, ethers, amines, acids, aldehydes, ketones, esters,halides, cyanides, sulphides, polyhydric alcohols, anhydrides such asphthalic and nitro compounds; of which the following are examples:

n-Decane n-Decyl alcohols n Decyl amines n-Decyl esters n-Decyl' halidesn-Decanoic acids n-Decyl ketones n-Decyl 'aldehydes n-Decylcyanidesn-Decyl sulphides Preferred examples of suitable, organic dryingmediums are creosote, petroleum distillates, coal tar, wood tar or wooddistillates, and the following:

High boiling alcohols:

Amyl Isopropyl Isobutyl Diethylene glycol Glycerol Aldehydes:

Butyric aldehyde Benzaldehyde Crotonaldehyde Furfural High boilingamines:

. Aniline Dimethyl-aniline Mono-, diand tri-ethanolamines PyridinesQuinollnes High boiling esters:

Butyl acetate Amyl acetate Butyl lactate DlbutylphthalateDiamylphthalate Glycol monoetnyl ether acetate Isopropyl lactate Octylacetate Diglycololeate Glycol stearate High boillng ethers:

Diamyl ether Diethylene glycol monoethyl ether Halides:

Chlorobenzenes Chlorinated phenols NitrochlorobenzenesOrtho-dichlorobenzenes Ortho-nitrochlorobenzenes Para-dichlorobenzenesNitro compounds:

Nitrobenzene Ortho-nitrotoluenes Hydrocarbons:

Benzenes Toluenes Mesitylenes Cumenes Naphthalenes DiphenylKetonesBenzophenone Furfural or other resin forming material may be usedas the drying medium if it is desired to leave in the wood resinouscondensation products, i. e., to incorporate a synthetic resin in thewood.

In the manufacture of hydrolyzed products, by means of acid hydrolysis,in accordance with this invention, from coinminuted Wood the material iswetted with a solution of a mineral acid, e. g., sulfuric acid of about1% strength and subjected in a rotating basket in 'a closed cyiim der tothe action of steam at a temperature of 340 to 360 F. (105 to 135lbs/sq. in. gauge pressure) for a period of 20 to 40 minutes, dependingon the particle size of the commlhuted wood and the lignin contentdesired in the final product. The steam pressure is then releasedthrough a line in the bottom of the treating cylinder so thatcondensates and drainings from the WOOd, which contain sugars, furfural,and other by-products are forced into a condensate flash tank in whichthere is a line in the vapor space leading to the atmosphere. Byreleasing the pressure in the flash tank to the atmosphere thehydrolysis liquor containing sugars and non-volatile substances isconcentrated. The steam being released is lead through suitable heatexchangers both for the purpose of recovering heat and steam volatilehy-products such as furfural and acetic acid by condensation.

When the pressure in the cylinder has reached atmospheric, wash Watermay be introduced and the hydrolyzed wood product washed by rotating thebasket. After each washing period the Wash water is drained 01f and aspray of Wash Water directed on the rotating basket from a spray lineprovided in the cylinder. washings in the manner described are continueduntil the hydrolyzed product is free of hydrolyzing acid and products orhydrolysis. A. satisfactory indication of this point is when a distilledwater sample in which a sample of thehydrolyzed wood has been boiledsnows a pH of 5.0 to 6.0.

The washed hydrolyzed product may then be vapor dried in the samecylinder by subjecting it to the action of the vapor from a boilinghydrocarbon, such as Stoddard solvent,'or other suitable organic dryingor drying and impregnating medium, introduced to the cylinder whilerotating the basket. The solvent may be removed if desired after dryinghas been completed by employing a suitable vacuum step.

In the accompanying drawings, I have illustrated a preferred apparatus,but it is to be understood that this apparatus may be suitably modifiedin order to carry out the invention within the scope of the appendedclaims.

In the attached drawing there is shown diagrammatically the apparatuswhich I employ for processing of Wood or Wood products with thevapor-liquid method for the production of hydrolyz'ed wood.

In the drawing A is a horizontal metal retort or cylinder such as, forexample, a creosoting cylinder. B is a cylindrical basket-like containerfor Wood shavings, sawdust, chips or similar mechanically disintegratedWood substance. This basket is constructed of Wire mesh of suitable sizecovering a rigid frame work l9. Spiral baffies H are arranged withinthis frame work to aid in mixing the material when the basket isrotated. The numeral l2 indicates an engaging device such as a femalegear to accommodate a gear I3 on the shaft M which passes throughpacking gland [5 to the sprocket i6 driven by a chain I! from motor [8and serves as a means for slow speed rotation of the basket B. Thenumeral l9 indicates a bearing on the cylinder B which receives thestationary shaft 20 on the door of the retort. When the door of theretort is-closed the shaft 28 and bearing I9 support the cylinder B incooperation with the rotating supporting means [Sand l4.

Rollers 21 supported on cylinder A, Whichcontact circular tracks orhands 22 forming part of frame work 18 on cylinderB, serve to align andsupport the basket during rotation. Suitable lever "operated rollers(not shown) may also be arranged for shifting to contact longitudinalbands '23 of frame work l8 and thus support basket B for loading orunloading from chamber A.

The cylinder A is connected through ports a, b and c to vapor line LVIwhich connects through valve 24 to evaporator or boiler C. The nipplesfrom the line LVI through ports a, b and c are extended into thecylinder about 4" to prevent drain back: of condensate in the cylinderto line LV!. Through ported, e and f the cylinder is connected to vaporline LV-2 having valves 25 and 26 to line LV-3 leading to dephlegma'torD or the 7 cylinder is connected pump 29. 1 1

evaporator into line HL2 and returns to the The following example isillustrative ofthe manner of using this apparatus to produce hydrolyzedwood of high lignin content.

Comminuted wood, e. g., wood chips having a havingvalve Sl by a pump,not shown, through valve 32, pump 33, and valve 34 to spray line SLl andspray header 35; the acid solution being sprayed on the basket and itscontents during slow rotation of the basket. When the comminuted wood inthe basket has-been saturated to'the desired extent withacid, as may bedetermined by gauging the tank from which the acid is beingdrawn, thepump is stopped and valves 3], 32 and 34 areclosed. During the sprayingoperation any of the acid solution not takenup by the wood may beallowed to drain from the cylinder to tank, F by opening valve 36 online LL- -l. It may then be returned to storage by opening valve 3! online LLII, by a suitable pumping means, not shown. Thecylinder A is thenconnected to the atmosphere through line LV2 by opening valves and 21 tocondenser E and valve 33 on line LV5. Steam is then introduced to, thecylinder from the evaporator C :(which in this case may be a simplesteam boiler) by opening valve on line LV I. Assoon as I the air in thecylinder has been displaced by the steam, as will be shown by live steambeing discharged from line LV5, valves 25, 21, and 38 arethen closed.Valves 39 and M are then opened, the steam passing from the evaporatorthrough lines LVI, LV--2 to the cylinder A. Steam pressure in'thecylinder A thereby rapidly ,in'creased to 195-135 lbs/sq} in;, whichusually requires fromB to 5 minutes During this time" the basket B iskept rotating at a rate of Std 15R. P. M. Valve 36 is partially openedto allow condensate containing reaction products from the'wood to draininto condensate tank F,

'valve t! on line LV -S being openedto condenser In. this mannercondensates from thecylin der A is being continually removed from thehydrolyzing theater and is being concentrated in tank F by the flashingoif of steam and steam volatile products to the condenser E which may beoperating also as a heat exchanger to recover heat from the steam. 'Inlieu'of the manually operated drain valve 33am automatic condensatedischarge trap may be employed to transfer the condensate fronr'thecylinder A to'th'e conden'sate tankF.

The conditions of temperature (340 F. to 360 F.) and pressure (195 to135 lbs/sq. in.) are maintained in the cylinder for the necessary timedried usingthe apparatus shown in the attached required to give thedesired lignin content in the final product. About 20 to 30minutesunder'the operating conditions described above will yield aproduct having a lignin content of 40 to 45%.

At the endof .this' time valves 39 and 49 are suitable. storage, notshown, by means of a pumping means, not shown, entering the heatexchanger D through line LL-Z and passing through the. tube section of Dto a suitable discharge line, not shown, returning to the wash waterstorage. 1

4 Condensate forming in.D may be allowed to fill that heat exchanger andspill over to condenser E by opening valve 43 on line LV-l2.

Condensation of steam and steam distilled byproducts from the woodoccurs in condenser E when water is introduced to the tube section ofthat condenser by suitable means, not shown. The condensate is collectedin condensate receiving tank H and may be transferred therefrom to avolatile by-product storage or tosuitable fractionating equipment, notshown, through line LL5 having valve 44.

Release of pressure from the cylinder A is usually completed in a matterof from 5 to l 10 minutes. 7

When the pressure in the cylinder A has 1 reached atmospheric, heatedwash water at a temperature of to F. is pumped into the cylinder from asuitable source through line LL9, having valve 3i, valves 32' and 35being opened. The wash water enters thecylinder quire about30 minutes tol'hour, the wash water,

is drained from the cylinder by opening a suitable discharge, not shown,onthe bottom of the cylinder. At the-end-of such periods of drainingwash water may be sprayed on the basket and contents and the latterallowed. to drain for a short period thereafter before introducing waterfor the next. main washing cycle.

a About 3 or- 4 such washinQg-cycleswill be found sufficient to removethe acid and hydrolysis prod ucts, a total of 10 to 15 thousand gallonsof wash water per ton of dry hydrolyzed wood, delivered in 3 or 4wash-ing'cycles, are required for the, washing. a a

The damp hydrolyzed product is then vapor ap the dedrawing in accordancewith. the methods scribed in my Patent No. 2,273,039 and my plicationSerial No. 579,851. 7 Operation of apparatus for drying is the same asthat scribed in the application SerialNo. 579,851 cept that the wood iscontained in a rotating basket instead of on trams which applies in thecase of massive wood.

The apparatus shown in the drawing may be used for hydrolysis of wood byvapor treatment with water acidified with small amounts of H61 toprepare it for subsequent treatment with aniline andfurfural to produceligno-cellulose plastic molding powders as described in U. S. Patentsluv- VA Nos. 1,923,756 and1-.,932,255.. After hydrolysis. the materialmay be washed in. the. cylinder B and subsequently dried by introducing.vaporized; aniline or furfural. Drying by means; or. aniline.- or analdehyde in vapor phase. gives. a much. more thorough. and. uniform.distribution of: the plasticizer throughout. the. mass and the heatingof the wood. at the; boiling pointof. the chemicals produces a much morestable ligninecelluiose aniline complex, or lignin-cellulose-iuriuralplastic when the material is molded. I

In preparing hydrolyzed: products from. either massive timber orcomminuted. wood. according. to the present. inventiom. where:- drying.is resorted. to, this is carried outv in accordance with my aforesaidpatent and. applications to substantially zero moisture content.

The hydrolyzed products obtained, whether from massive timber orcomminutedwood, are completely dried and are identifiable because theyare substantially devoid ofwater soluble extracts such as hexose sugarsand furi'uralproduced by the hydrolysis action. Moreover the hydrolyzedproducts are further identifiable by being substantially devoid oforganic solvent soluble extractives such as Wood gums and resins, eithernormally present or produced by said hydrolysls because these areremoved when the treated wood is completely dried with an organic vaporwhich is a solvent for such extractives.

To the dried comm-muted wood treated as above there may be incorporateda potentially reactive synthetic resin. Among such resins are thoseobtainable from phenol-aldehyde, aminealdehyde, urea-aldehyde, Glyptaland cumarone resin com onents. Prererably about 2: by weight or thepotentially reactive synthetic resin is introduced to the comminutedwood which may in some cases be further reduced in size so as to passthrough a 20 mesh screen or smaller. In this manner a heat moldable orheat compressible composition is formed.

It will be observed that condensates from. the steam and products of thehydrolysis reaction soluble therein are continually removed as formedfrom contact with the. wood and by removing these condensates from thetreating chamber and lowering the pressure. and temperature conditionssurrounding them, for example as in the flash tank F, the usualdegradation which occurs when these products are left in the.environment of the treating conditions in. the chamber A is largelyprevented and the by-products. are in a much more usable and valuableform.

After the hydrolysis treatment the; wood is usually washed with waterand in the case of comminuted wood as much water expressed there.- fromas possible before the same is: introduced to the vapor phase drier.This vapor phase drying with an organic vapor. as set forth. in my abovementioned patents, not only produces a completely dry wood but, asmentioned above, removes the organic solvent soluble extractivesproduced by the hydrolysis, or already present in the wood. These woodgums, although. being resinous in nature, are, as a. rule, not generallymiscible with synthetic resins and hence will deter the latter fromreadily wetting and penetrating the wood in the most satisfactory mannerand furthermore such wood resins are generally hygroscopic in nature.although not water soluble and hence are poor binding agents. Thereforeit is desirable that these wood gums or resins be removed.

Jlclaimti Y i j 1. The process of hydrolyzing wood which comeprisesz:treatingthe: wood in a. closed chamber; with steam in the. presence. ofan acid catalyst and simultaneously with. hydrolysis: of the Wood:removingirom said chamber the condensate. from the steamandproductsofthe hydrolysis reaction soluble therein.

2-. The process of. hydrolyzing, wood which. com.- prises treating thewood in a closed chamber with steam in. the presence of. an acid.catalyst-and simultaneouslywith hydrolysis of the woodremoving from saidchamber the condensatesfrom.

the steam and. products of the. hydrolysis reaction soluble therein, andthereafter removing organic solvent soluble extractives. produced bythe. hydrolysis together with such extractives already present in. thewood while; drying to. zero moisture content with an organic solventvvapor.

is The process. of hydrolyzing wood. which comprises. treating the same.in comminuted COIldie tionin. a closed. chamber with steamin thev pres.-ence of an acid. catalyst and simultaneously with hydrolysis. ofthe-wood removing from said chamber the condensates. from the steam andproducts of the hydrolysis reaction soluble therein, washing said?hydrolyzed wood. with water, and there after removing organic solvent:soluble. extractives produced by the hydrolysis together with such 1extractives already present in the wood while drying to zero. moisturecontent with an organic solvent vapor. a

4. The process of hydrolyzing wood which oomprises treating the same incomminutedcondition in a closed chamber with steam in the presence of anacid catalyst and simultaneously with hydrolysis of the wood removingfrom said cham ber the condensates from the steam and products of thehydrolysis reaction soluble therein and recovering the said by-products'of the hydrolysis continuously as formed during hydrolysis of the wood,washing said hydrolyzed wood with water, and thereafter removing organicsolvent soluble extractivesproduced by the hydrolysis together with suchextractives already present in the Wood while drying to zero moisturecontent with an organic solvent vapor.

5. The process oftreating wood which comprises wetting the wood with adilute mineral acid, subjecting th wood in. a. closed chamber to theaction of live steam and simultaneously with said treatment of the woodremoving from contact therewith the. wood condensates and reactionproducts of the treatment soluble in said condensates, subjecting thetreated Wood to washing with. water, expressing the. Water from thewashed and. treated wood, and drying-the washed and treated wood in thepresence of an organic drying medium in vapor phase which is a solventfor. the organic solvent soluble. products produced by the. treatmentas. well as such products already present in the wood.

6-. A. wood treatmentv process. comprising wet.- ting disintegrated woodparticles with a dilute mineral acid, subjecting said wood particles,in. a closed chamber to the action of live steam, maintaining said steamtreatment at atemperature of about 340 F. to 36.0 F. for a timesufficient to give the desired lignin content in the treated wood,washing the time treated wood particles with water to remove the watersoluble reaction products therefrom, and drying; the washed woodparticles. with heated, inert. organic vapor which removes the remainingwater and the organic solvent solubles from the wood and efiectsthorough drying of the wood.

7 7. A process of treating wood to render it suitable for resinimpregnation, comprising wetting the wood with a dilute solution of amineral acid, subjecting the wood in a closed chamber to the action oflive steam, continually removing the wood condensates and reactionproducts soluble therein from said chamber so as to avoid degradationthereof, continuing the steam treatment until the desired lignin contentin the wood is obtained, washing the thus treated wood with water toremove water solubles, and then drying the washed wood by passingthrough said chamber a flow of highly heated, inert, organic dryingvapor that removes the moisture and the organic solvent solubles fromthe wood.

8. A process of treating wood to render it suitable for resinimpregnation, comprising wetting the wood with a dilute solution of amineral acid, subjecting the woo-d in a closed chamber to the action oflive steam at a pressure of about 105- 135 pounds per square inch,continually removing the wood condensates and reaction products solubletherein from said chamber so as to avoid degradation thereof,maintaining the steam treat ment at a temperature of about 340 F. to 360F. until a lignin content of about 40% to 45% in the wood is obtained,washing the thus treated wood with hot water to remove water solubles,repeating this washing treatment a plurality of times and removing thewash water from the chamber, and then drying the washed wood by passingthrough the chamber a flow of highly heated,

inert, organic drying vapor that removes the moisture and the organicsolvent solubles from the wood.

MONIE S. HUDSON.

REFERENCES CITED The following references are of record in the file. ofthis patent:

UNITED STATES PATENTS Number Name Date 150,111 Voelter Apr. 21, 18741,037,185 Gallagher et al. Aug. 27, 1912 1,059,820 Besenfelden Apr. 22,1913 1,087,743 Ekstrom Feb. 17, 1914 1,890,304 Scholler Dec. 6, 19322,080,077 Howard May 11, 1937 2,108,567 Scholler Feb. 15, 1938 2,123,211Scholler July 12, 1938 2,123,212 Scholler July 12, 1938 2,153,316Sherrard Apr. 4, 1939 2,156,160 Olson Apr. 25, 1939 2,196,277 SchorgerApr. 9, 1940 2,315,372 Kressman Mar. 30, 1943 2,323,194 Beveridge June29, 1943 2,325,570 Katzen July 27, 1943 FOREIGN PATENTS Number CountryDate 435,896 Canada July 23, 1946 OTHER REFERENCES Katzen et a1: Ind.Eng. Chem., pp. 314-322, vol. 34, No. 3 (Mar. 1942).

8. A PROCESS OF TREATING WOOD TO RENDER IT SUITABLE FOR RESINIMPREGNATION, COMPRISING WETTING THE WOOD WITH A DILUTE SOLUTION OFMINERAL ACID, SUBJECTING THE WOOD IN A CLOSED CHAMBER TO THE ACTION OFLIVE STEAM AT A PRESSURE OF ABOUT 105135 POUNDS PER SQUARE INCH,CONTINUALLY REMOVING THE WOOD CONDENSATES AND REACTION PRODUCTS SOLUBLETHEREIN FROM SAID CHAMBER SO AS TO AVOID DEGRADATION THEREOF,MAINTAINING THE STEAM TREATMENT AT A TEMPERATURE OF ABOUT 340* F. TO360* F. UNTIL A LIGNIN CONTENT OF ABOUT 40% TO 45% IN THE WOOD ISOBTAINED, WASHING THE THUS TREATED WOOD WITH HOT WATER TO REMOVE WATERSOLUBLES, REPEATING THIS WASHING TREATMENT A PLURALITY OF TIMES ANDREMOVING THE WASH WATER FROM THE CHAMBER, AND THEN DRYING THE WASHEDWOOD BY PASSING THROUGH THE CHAMBER A FLOW OF HIGHLY HEATED, INERT,ORGANIC DRYING VAPOR THAT REMOVES THE MOISTURE AND THE ORGANIC SOLVNTSOLUBLES FROM THE WOOD.